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author | Lukas Stadler <lukas.stadler@jku.at> |
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date | Fri, 06 May 2011 10:25:37 +0200 |
parents | 16b9a8b5ad39 |
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/* * Copyright (c) 2009, 2010, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package com.sun.c1x.opt; import com.sun.c1x.*; import com.sun.c1x.ir.*; /** * The {@code ValueMap} class implements a nested hashtable data structure * for use in local and global value numbering. * * @author Ben L. Titzer */ public class ValueMap { /** * The class that forms hash chains. */ private static class Link { final ValueMap map; final int valueNumber; final Instruction value; final Link next; Link(ValueMap map, int valueNumber, Instruction value, Link next) { this.map = map; this.valueNumber = valueNumber; this.value = value; this.next = next; } } private final ValueMap parent; /** * The table of links, indexed by hashing using the {@link Instruction#valueNumber() method}. * The hash chains themselves may share parts of the parents' hash chains at the end. */ private Link[] table; /** * Total number of entries in this map and the parent, used to compute unique ids. */ private int count; /** * The maximum size allowed before triggering resizing. */ private int max; /** * Creates a new value map. */ public ValueMap() { parent = null; table = new Link[19]; } /** * Creates a new value map with the specified parent value map. * @param parent the parent value map */ public ValueMap(ValueMap parent) { this.parent = parent; this.table = parent.table.clone(); this.count = parent.count; this.max = table.length + table.length / 2; } /** * Inserts a value into the value map and looks up any previously available value. * @param x the instruction to insert into the value map * @return the value with which to replace the specified instruction, or the specified * instruction if there is no replacement */ public Instruction findInsert(Instruction x) { int valueNumber = x.valueNumber(); if (valueNumber != 0) { // value number != 0 means the instruction can be value numbered int index = indexOf(valueNumber, table); Link l = table[index]; // hash and linear search while (l != null) { if (l.valueNumber == valueNumber && l.value.valueEqual(x)) { return l.value; } l = l.next; } // not found; insert table[index] = new Link(this, valueNumber, x, table[index]); if (count > max) { resize(); } } return x; } /** * Kills all values in this local value map. */ public void killAll() { assert parent == null : "should only be used for local value numbering"; for (int i = 0; i < table.length; i++) { table[i] = null; } count = 0; } private void resize() { C1XMetrics.ValueMapResizes++; Link[] ntable = new Link[table.length * 3 + 4]; if (parent != null) { // first add all the parent's entries by cloning them for (int i = 0; i < table.length; i++) { Link l = table[i]; while (l != null && l.map == this) { l = l.next; // skip entries in this map } while (l != null) { // copy entries from parent int index = indexOf(l.valueNumber, ntable); ntable[index] = new Link(l.map, l.valueNumber, l.value, ntable[index]); l = l.next; } } } for (int i = 0; i < table.length; i++) { Link l = table[i]; // now add all the entries from this map while (l != null && l.map == this) { int index = indexOf(l.valueNumber, ntable); ntable[index] = new Link(l.map, l.valueNumber, l.value, ntable[index]); l = l.next; } } table = ntable; max = table.length + table.length / 2; } private int indexOf(int valueNumber, Link[] t) { return (valueNumber & 0x7fffffff) % t.length; } }